So if I have the following requirements and must use Bing for background mapping, directions etc, am I right in my understanding of the tools available;

Birds eye (is only available using Bing Extension)

Load and Toggle Dynamic service layers (is only available using JS API). Note I have tested this script http://arcscripts.esri.com/details.asp?dbid=16066 but although I can add DMSLayers through Bing Extension, I am not able to manipulate them because several properties e.g layerInfos are only available after esri.Map maps.AddLayers has been called.

Bing Map control (is only available using Bing Extension, although I could fudge a replica in JSAPI)

Streetside (is not available in both unless I use silverlight)

On the fly data projection (is only available using JS API)

In short my problem is which API satifies my requirements but not requiring a plug in so Silverlight and Flex are out of the question.

Any additional feedback on your last post? I agree and have been very unimpressed with the lack of uniformed information regarding the Bing Extension (the link the SDK doesn�??t work). I have only been researching this topic for a day or so, but I am not even sure how to access the Bing Maps Extension.

Our agency has standardized our API framework as JS API and dojo. We have recently started to use the Bing Maps key to reference the Bing basemaps. However, we have other developers in other sections that are using the Bing Maps Ajax V7 API and it is unclear to me if those developers can leverage any the Bing Extension for ArcGIS.

The bing extension is a different product than the ArcGIS API for JavaScript. The bing extension is retired and relies on an older version of the bing maps SDK. We are not going to be updating it going forward. I apologize that this is not clear.